Data processing systems, such as the 2200 series systems from Unisys, include one or more instruction processors, a memory arrangement, and one or more input/output processors (IOP) that handle IO requests for input or output of data for the system. IO requests reference data that is input or output on IO channels such as SCSI, fiber, or a via a network, for example.
In the course of developing a system and bringing the system to market, various tests are performed in an attempt to ensure that the system functions according to specifications. Problems may be identified by comparing data generated by the system in running a test to expected result data. If a problem is detected, further testing may be performed to identify the source of the problem. In performing the further testing additional data may be gathered at various times during the course of the testing for analysis. This “debug data” may be useful in tracing operations performed by the system, ruling out possible problem sources, and eventually isolating the problem source.
Gathering IOP-related debug data may be inconvenient because the IOP has traditionally been implemented as a IC arrangement. For example, IOP monitoring may require a hardwired connection to the circuitry of the IOP. Also, an IOP being micro-code driven would require code that generates debug data along with the code that implements the mainline processing of the IOP. A method and apparatus that addresses these and related issues would therefore be desirable.